Area lakes had been reluctant to freeze early this winter. But the recent cold has accelerated ice formation.
The freezing of open water is as complex as it is fascinating.
The Earth under the ice is warm, which creates an interesting calculus problem as cooling rates from cold air do battle with heat rising from below. Adding to the mystery is the fact that water reaches maximum density at 39 degrees. So as soon as the surface of the water reaches 39 degrees, it sinks and is replaced by warmer water from below. This process continues until the entire system is colder than 39 degrees and, only then, can the lake begin to freeze.
This is part of why shallow lakes freeze much more quickly. Once ice forms, it acts as an insulator, which slows the thickening of the ice.
Snow cover on top of the ice is an even better insulator and can greatly restrict ice formation underneath.
